/* =============================================================
 * Your Grandmother's guide to Algorithms
 * =============================================================
 *
 * Copyright (c) 2007, Saverio Miroddi
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright 
 *       notice, this list of conditions and the following disclaimer in the 
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the SaverioMiroddiSoftware nor the names of its 
 *       contributors may be used to endorse or promote products derived from 
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *  
 * ---------------------------
 * BitPath.java
 * ---------------------------
 *
 */
package huffman;

import java.util.Arrays;

/**
 * Trivial implementation of a bit storage class; JDK BitSet is inappropriate
 * for this purpose.<br>
 * It's interesting to use more fragile routines to discover more easily bugs
 * around.
 * 
 * @author Saverio Miroddi
 */
public class BitPath
{
	private boolean[] _bits;
	private int _writePtr;
	private int _readPtr;
	
	public BitPath()
	{
		_bits = new boolean[8];
		_readPtr = 0;
		_writePtr = 0;
	}

	/**
	 * Copy contructor; copy read/write pointers too.
	 */
	public BitPath(BitPath bitPath)
	{
		_bits = bitPath._bits.clone();
		_readPtr = bitPath._readPtr;
		_writePtr = bitPath._writePtr;
	}

	public void append(boolean newBit)
	{
		// == -> more fragile
		if (_writePtr == _bits.length)
			_bits = Arrays.copyOf(_bits, _bits.length * 2);

		_bits[_writePtr++] = newBit; // ++
	}
	
	public void removeLast()
	{
		if (_writePtr == 0) throw new ArrayIndexOutOfBoundsException();
		
		_writePtr--;
	}

	/**
	 * Read is separate from writing, so that a write can be done first, then a
	 * read.
	 */
	public boolean read()
	{
		return _bits[_readPtr++]; // ++
	}
	
	public boolean[] getBits()
	{
		return Arrays.copyOf(_bits, _writePtr);
	}
	
	@Override
	public String toString()
	{
		String buffer = "";
		
		for (int i = 0; i < _writePtr; i++)
			buffer += _bits[i] ? '1' : '0';
		
		return buffer;
	}

	public int length()
	{
		return _writePtr;
	}
}